In renal transplant patients hepatitis B infection is associated with a higher morbidity and mortality. Therefore, we investigated the immunogenicity of an enhanced vaccination scheme with a recombinant DNA hepatitis B vaccine in renal allograft recipients. Injections of 40 micrograms were given at months 0, 1, 2 and 6. Conversion rate (anti-HBS antibody titre > 10 mIU ml-1) was only 36%. On the other hand, in patients vaccinated before transplantation, a booster injection of 40 micrograms was highly successful, resulting in a rise of antibody titre > 10 mIU ml-1 in 86%. In view of the poor vaccination results after transplantation, we strongly recommend hepatitis B vaccination prior to transplantation.